When the iPhone debuted in 2007, developers who wanted to build apps for Apple’s smartphone had just one option—make a Web app that users would access through the phone’s built-in Safari browser. “We’ve come up with a very sweet solution,” Apple CEO Steve Jobs said at the time, hailing the Web-based approach as an “innovative new way to create apps for iPhone.”

Four years later, some iOS developers finally seem to be embracing that approach—even though Jobs might now prefer that they instead avail themselves of the full App Store experience.

What’s behind the steady increase in prominent iOS-focused Web apps when there’s a perfectly good—and thriving—App Store for pushing wares to iPhone, iPod touch, and iPad owners? A leading cause may be Apple’s own rules about App Store offerings.

Apple offers developers an iOS SDK to create mobile apps. But some are opting for Web-based apps optimized for Apple’s mobile devices.

Apple, as you remember, relented on its Web-based approach to mobile apps in 2008, opening the App Store and giving developers a chance to build native programs for the iPhone. App makers, lukewarm to the original Web-based approach, embraced the iPhone SDK and the App Store model—even if it meant agreeing to Apple’s very detailed restrictions and occasionally lengthy review process.

But a few new wrinkles have sprung up in recent months that have some notable developers hoping that there’s more than one way to make money with iOS apps. And those wrinkles stem largely from Apple’s policies on subscription-based apps.

When Apple unveiled iOS subscriptions this past February, the company mandated that developers hand over 30 percent of all sales back to Apple, just as they do with app purchases. Apple also insisted that in-app purchases must be priced at or below the prices of the same good sold elsewhere—a tough pill to swallow for some publishers. Finally, Apple required that any digital content available for purchase to enhance an app—like, say, an ebook—must also be offered through Apple’s official in-app purchasing system. In Amazon’s case, that rule meant that the company would need to find some way to add its 950,000 ebook titles into Apple’s in-app purchasing program—an impossible task given Apple’s current developer tools.

The result of these rules: Ebook apps can’t link back to their ebook stores. Customers either must know or independently discover the URLs for those stores and access them directly. And each time an app maker wants to update a product, it’s subject to another round of Apple’s approval process. Apple has also demonstrated that it retains the right to update (and re-update) its App Store policies at any time—and apps will need to comply or face eviction from the store.

So what’s a developer to do? While many app makers do just fine with the rules Apple has put into place, others are finding the restrictions a little too limiting. And so you get Amazon launching the Kindle Cloud Reader Web-based app.

Amazon’s Web app doesn’t just include a link to the Kindle Store—which, again, the Kindle iOS app is not allowed to feature—it includes an excellent iPad-optimized Kindle Store browsing experience. Browsing the store is better with the Web app than with Amazon’s desktop website. For finding and buying ebooks from an iPad, it’s certainly the best option. Amazon can update the Kindle Web app whenever it wants to, with no approval process hold-ups, and no external restrictions on what the app can and can’t do.

But in launching its Kindle Cloud Reader app on the Web, Amazon didn’t pull the native Kindle app from Apple’s App Store. For the time being at least, the two apps will coexist. That may be because the Web app’s reading experience pales in comparison to the native app. It may also be because iOS device owners are well-trained to visit the App Store—and not Safari—to discover new apps, and that Amazon feels it can’t afford to not have the Kindle app in the App Store.

Amazon’s not alone. The Financial Times, too, maintains an App Store presence in addition to its Web app. Far fewer companies seem to be taking the Vudu’s route of exclusively offering a Web app, without a corresponding App Store entry.

It’s worth noting that all of these Web apps are free to use, at least at first. Each makes its money through the Web equivalent of in-app purchases—Amazon with its books, The Financial Times with its subscriptions, and Vudu with its pay-per-view purchases. Web apps likely seem less appealing to folks developing entirely free apps, or free apps that rely solely on in-app advertising to make their money: Apple’s not raking the 30 percent off the top, and it’s still got the best iOS device distribution in town.

Could more app makers embrace the Web model over Apple’s store? There are certainly reasons for developers to go that route. Web apps can work offline with HTML5 storage, they can place app-like icons on your homescreen, and they can do things App Store apps can’t do. Want to browse the complete archives of Playboy magazine? There’s an app for that—but it’s Web-only.

If app makers and publishers continue to innovate on the Web app side—bypassing not just Apple’s rules but also the need to pay it that 30 percent commission—how will Cupertino respond? Though Apple once proudly embraced Web apps as not just a great way, but the only way to develop for iOS, the company hasn’t updated its list of iOS-friendly Web apps since December 2010. And while a company as profitable as Apple probably wouldn’t fret over losing out on the 30 percent take it might otherwise get from some apps were they on the App Store, it’s important to remember that Apple is staffed not just by creative geniuses, but by shrewd business minds, too.

Thus, if Web apps truly take off—a big “if,” given that the App Store comes pre-installed on every device with access to hundreds of thousands of apps—and Apple becomes unhappy with the native-to-Web-app evolution, the company will surely find a way to halt that theoretical App Store exodus—likely by loosening the App Store’s rules.

My bet, however, is that Apple isn’t really miffed at all by Amazon or Playboy and the others. By creating their impressive Web apps, these companies are proving Apple’s long-standing line that such apps are indeed a viable alternative to the App Store. Apple can continue offering the curated experience its sensibilities demand and, whenever the next inevitable App Store controversy arises, it can, in its defense, proudly point to the fully acceptable “other way” embraced by several prominent companies.

Apple’s position is easy to understand: There would be no iOS app market were it not for iOS, and the company can therefore run its App Store however it likes. Apple’s quite content for customers to think that it’s easier to just use the iBooks app—with its exempted, permitted built-in bookstore—than fiddle with Amazon’s native or Web apps. To Apple, then, the slow-paced rise of decent iOS Web apps is a win-win: It proves the company’s point that such apps are a realistic App Store alternative, and the company can reverse course at any time should it feel that the App Store model is in any way threatened. My guess is that any such threat is a long way off.

[Lex Friedman is a Macworld staff writer.]

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